1. Field of the Invention
This invention relates to a drilling fluid dispersant having improved temperature stability, dispersing properties and "solids contamination" tolerance.
2. Description of the Prior Art
U.S. Pat. No. 2,552,775--Fischer et al, issued May 15, 1951, describes a water based clay drilling fluid containing an alkali metal or ammonium polyacrylate salt having a molecular weight greater than 2,000 as a protective agent for controlling filtration rates, viscosities and other properties as well as preserving and/or increasing producing formation permeabilities.
U.S. Pat. No. 2,603,598--Meadors, issued July 15, 1952, describes a water based clay drilling fluid containing sufficient alkanolamine to increase pH to at least 10 without unduly increasing viscosity.
U.S. Pat. No. 2,718,497--Oldham et al, issued Sept. 20, 1955, describes a water based clay drilling fluid containing a linear hydrocarbon chain polymer acid salt such as a polyacrylic acid salt having a molecular weight greater than 10,000 to control water loss. The salt is produced by reacting alkali metal hydroxide, ammonium hydroxide or an alkanolamine with the acid.
U.S. Pat. No. 4,370,171--Robinson et al, issued Jan. 25, 1983, describes a method for dispersing a comminuted solid in aqueous medium using a salt of alkanolamine and polymeric carboxylic acid. Polymeric carboxylic acids such as polyacrylic acids may be used.
U. D. Mamadzhanov et al in Tr. VNII Ekon., Organiz. Proiz-Va I Tekhn.-Ekon. Inform. V Gaz. Prom-Sti (1974) 114-117 describe synthesis of chemical reagents based on acrylic polymers and aminoalcohols. A study of these reagents on clayey solutions has shown that they may find practical application in deep well drilling.
Japanese Patent Public Disclosure No. 60-133085--Nippon Oils and Fats KK published July 16, 1985 describes a mud additive to improve heat, salt and cement resistance of a water based clay drilling fluid. The additive may be (a) polyacrylic acid having a 1000-20,000 molecular weight or (b) an alkali metal, ammonium or alkanolamine salt of (a) having a degree of neutralization of 30% or less.